Synthetic indigo in a new form and process of making same.



'from the-.benzyl group. Now I have further benzoic acids,eryLQXy-ecetic acids, benzyl digo and capable of directly yieldinginleuco compounds.

UNITE STi'lES PATENT OFFICE.

ALBRECHT SCHMIDT, OF HCHST-ON-THE -MAIN, GERMANY, ASSIGNOR TO FARE-WEBXE VORM. I IEISTEB LUCIUS & BRfiNING, 0F HijCI-IST-ON-THE-MAIN, GER-MANY, A GORPORATION 0F GERMAHY.

SYNTHETIC INDIGO IN A HEW FORM AND PROCESS OF MAKING SAME.

No Drawing. Application filed August 15,

Specification of Letters Patent.

Patented Apr. 1, 1913. 1910. serial No. 577,200.

To all whom it may concern Be it known that I, ALBRECHT SCHMIDT, Ph. D.,chemist, a citizen of the Empire of Germany, residing atliiichsooirtheMain, Germany, have invented certain new and usefulImprovements in Synthetic Indigo in a New Form and Process of MakingSame, of which the following is e specification. In U. 3.. Patentapplication Ser. No. 576,703 filed August El, 1910 I have described aprocess according to which a new form of svnthetic indigo is obtained bycausing in igo to form in presence of aminosulfonic acids containingresidues derived found that the some property, namely that of producingindigo in this form, must be attributed to all aromatic acids (sulfonicacids, cerboxylic acids). For instance the following acids exercise aarticularly energetic action in this regard viz: LQ-naphtholsulfonicacid, 2.6, 1.7, 2.7 or 2.8 nephtholsulfonic acid,dimethylanilin-p-sulfonic acid, 1.5-naphthalindisulfonic acid,2-chloro-l-toluene-4-sulfouic acid, p-phenolsulfonic acid,G,,H,CH,SO,N2L, phenanthrenesulfonic acids, sulfonic acids derived fromcarhazole, rmthracene, etc, pand m-sulfoanthranilic acid, aryiglycinsand diglycins, salicylic acid and the like. But also other- :tromaticacids of simpler constitution show a remarkable action'uf employed inlarger quantities.

The formation and separation of the new indigo may be effected in themanner described in my specified application, namely, by subjectingindol derivatives which are closely related to indigo and capable ofdirectly ielding indigo, to indigo produc- 'ing con itions. By the termindol derivatives which are closely relzited to indigo, I primarily meanthe indigo salts, both those of the dyestufi itself and of its Thereforethe indigo is produced by dissociating indigo salts, for example,indigo-sulfate, with water, in pres ence of the above mentioned acids ortheir salts, whereby the new indigo is liberated; or by precipitatingwith air or another oxidizing agent sol lOIlS or phstes consisting ofincligo-leuco salts {indosylmllralh in acid is removed from the ingstirred the mass for about one-fourth.

or one-half hour it is poured on ice'. The operation may also be carriedout in inverse order by first Well cooling the mixture of indigosulfate,aromatic acid and sulfuric acid and gradually nddin to it dilutedsulfuric acid or ice, either 0 these a ents dissociating theindigo-sulfate into in igo with little evolution of heat. Thedissociation may also be effected in the presence of other bodies, forinstance of starch or any other insoluble or soluble carbohydrate or asimilur body, such as glycerin; further, in the presence ofvoluminousbodies' such as hydrates of silicic acid, etc. These bodiesbetter retain the colloid'like form of the indigo, in which it can beeasily made into a paste, and prevent it from changin into a form inwhich it can only with ditficulty be moistened and made into aaste withwater, and istherefore .more'di cult-1y reducible. The fine] -dividedacid dyestuffpaste thus obtained is passed through the filter-press andwashed until the sulfuric mess-cake; the presscake may then be furtwashed out or there may be added to it caustic soda lye, ammonia or asimilar neutralizing a nt until it becomes neutral or slightly a1 aline.The product thus obtamed possesses the property of being most ormoderately I substances, starch, etc.

less as the case may be) above mentioned acids, and this solution isprecipitated with air or agent.

The abovedescribed press-cakes may be allowed to dry in the air or theymay be dried u into lumps by exposing them to ex- .ternal eat;furthermore the water may be caused to evaporate in wwuaor by exposingthe mass to higher temperature so as to obtain a powder or small lumps;moreover the still moist or dry powder may pressed so as to form lumps.Finally, ere may be added inorganic or organicsubstances suitable formaintaining the indigo in the colloid form, such, as: china-clay,

kaolin, or the like, or glycerin, sugar-like another oxidizing The newproduct is broadly claimed my application Ser. ust 11, 1910. The dryproduct, specifieal in the form of powder, is claimed in m applicationSer. No. 708,481,filed Juy 9, 191-2.

Having now described my invention, what I claim is:

1. The process of making a new form of which consists in producsyntheticindigo,

indol derivatives which ing indigo from rectly yielding indigo, in thepresence of aromatic acids.

2. The process of making a new form of synthetic indigo, which consistsin producbeaain No. 576,703, filed Aug Y are closely related to indigoand capable pf diing indigo from indigo salts intliepresence of aromaticacids.

3. The rocess of making a new form of synthetic indigo, which consistsin producing indigo from leuco-indigo salts in the resence of aromaticacids. l 4. The recess of making a new form of synthetieindigo, whichconsists in pr ucing indigo from indol derivatives which are closelyrelated to indigo and capable of directly yielding indigo, in presenceof are v matic acids and solid diluents. 5. As a new product, the lumpsobtained from indigo in the new form, which new form is extremely easilyand .quicklyreducible inslightly reducing agcnts .and; when made up into2.7 'aste yields a deep uid,,which on, blue filtrate, through amicroscope indigo-particles can be discerned. :1

6. As a new product-,the mixture of lid diluents with indigo in the newform, which being put'on a p and in--which when seen new 'form isextremely easily and guiclrly I reducible in slightly alkaline reducing65 agents and,- when made up into a aste wi water, yields a dee ingliquid, which, on being put on a filter, 'ves a blue filtrate and inwhich, when seen through a'microscope, no more crystallineindigo-particles, can be discerned.

, In testimony ture in presence of two witnesses.- ALBRECHT SCHMIDT-h)Witnesse JEAN GRUND, CARL Gnono.

no, more rys tw p with water; 7. blue difiicu tly-de siting liq-. lter'giv'esa piblue difiicult y-depqeitewhereof, I atlix my signar Q

